A 240 sec shot of this Milky Way without star trails. From a favorite spot overlooking Monterey Bay.
It was shot with a DIY Barndoor Tracker which
allows you to shoot longer (wide angle )exposures and track the stars to compensate for the Earth's rotation

This industrial hinge, found at the big box hardware store, has the key dimension of 181 mm between the center of the hinge to the hand crank bolt.

Just roughly align the hinge to the North Star, point the camera to sky of interest and turn the hand crank to follow the second hand of an old analog watch.

The same shot with the 240 sec of star trails

And a website with a description of the barndoor tracker http://www.astropix.com/BGDA/SAMPLE2/SAMPLE2.HTM